Method for making evaporator or condenser construction

ABSTRACT

The method of making a refrigeration evaporator or condenser construction wherein the ends of preferably aluminum tubes which have been extended through heat exchange plates or fins in a refrigeration evaporator or condenser construction are joined with U-bend connectors, said method comprising forming radial internal beads near the ends of the tubes to be connected to provide stops for the ends of the U-bend connectors which are of lesser diameter, flaring the very end portions of the tubes to be connected, laying a thermo-fluid welding material around the connector end portions within the flared ends of the tubes to be connected, and applying heat to flow the said material prior to chilling.

United States Patent [1 1 Morris Aug. 7, 1973 [54] METHOD FOR MAKINGEVAPORATOR 0R CONDENSER CONSTRUCTION '75 Inventor: Herbert R. Mofi-fiiMorrisville, Pa. [73 Assignee: Emhart Corporation, Bloomfield? Conn. 1 221 Filed? 12, 1971 21 Appl. No.: 171,297

Related US. Application Data [63] Continuation of Ser. No. 737,080, June14, 1968,

3,397,445 8/1968 Ulmer et aim, 29/498 X 3,456,331 7/1969 Holden 29/47l.1

FORElGN PATENTS OR APPLICATIONS 1,108,851 4/1968 Great Britain.. 1/5

Primary Examiner-Richard Bernard Lazarus Attorney-McCormick, Paulding &Huber [57] ABSTRACT The method of making a refrigeration evaporator orcondenser construction wherein the ends of preferably aluminum tubeswhich have been extended through heat exchange plates or fins in arefrigeration evaporator or condenser construction are joined withU-bend connectors, said method comprising forming radial internal beadsnear the ends of the tubes to be connected to provide stops for the endsof the U-bend connectors which are of lesser diameter, flaring the veryend portions of the tubes to be connected, laying a thermofluid weldingmaterial around the connector end por- [56] References Cited tionswithin the flared ends of the tubes to be con- UNITED STATES PATENTSnected, and applying heat to flow the said material prior to chilling.1,931,467 10/1933 Young 285/157 X 2,303,949 12/1942 Nordell 285/157 X 9Claims, 6 Drawing Figures 2,460,667 2/ 1949 Wurzberger 29/479 3,205,5739/1965 Seal et a1. 29/479 X 3,334,925 8/1967 Jayne 29/488 x PATENTED NIB7 I975 FIG, 5

, FIG. 4

HERBERT R. MORRIS ATTORNEYS ,METIIOD FOR MAKING EVAPORATOR OR CONDENSERCONSTRUCTION CROSS-REFERENC E This is a continuation of application Ser.No. 737,080 filed June 14, 1968 for METHOD FOR JOINING TUBE ENDS, nowabandoned.

BACKGROUND OF THE INVENTION Coils or tubes in evaporators and condensersfor refrigeration apparatus are conventionally made of copper, withU-bend connectors of the same diameter. Each end to be connected isgenerally enlarged substantially with a mandrel or other expanding toolto form a socket to receive a connector end and a welding material. Theenlarging embeds impurities in the inner surface of the socket which maycause trouble, but do not because of burning away at the hightemperatures to which the copper can be subjected during welding,soldering or brazing.

Copper is often in short supply, and aluminum tubing is a desirablesubstitute except for the soldering, brazing or welding difficulties itpresents. That is, the welding temperature for aluminum must be lower,and the impurities embedded by the expanding tool remain to prevent asatisfactory joinder. This invention has been developed to overcomethese difficulties.

SUMMARY OF THE INVENTION According to the present invention there isprovided a method of manufacturing evaporators or condensers forrefrigeration apparatus comprising the steps of thrusting at least twoelongated main tubes, the ends of which have a mill stock finish,through heat exchange plates so that the said plates are mounted in agenerally parallel relationship on the main tubes, and connecting atleast one pair of ends of the main tubes with a generally U-shapedconnector tube having a mill stock finish. The ends of the connectortube are of such size relative to the ends of the main tubes that theU-shaped connector tube may have each of its two tube endstelescopically assembled with a respective one of the pair of main tubeends, thereby forming a connection consisting of two joints eachincluding one tube end inserted in another tube end. A radially inwardlydirected bead is formed on the larger diameter tube end of each proposedjoint, which bead is spaced from the adjacent open end of the largerdiameter tube end to define a socket between the open end and the bead.The socket has an inside diameter equal to the inside diameter of theremainder of the tube in which it is formed, and has an interior surfacehaving a mill stock finish. Each tube end of the connector tube istelescopically assembled with an associated one of the pair of main tubeends to bring the smaller diameter tube end of each joint into abuttingrelation with an associated bead. A bonding material is applied aroundeach end portion of the smaller diameter tube end of each joint andgenerally adjacent the open end of the larger diameter tube end of eachjoint. Each joint is then heated to cause the bonding material to fiowand thereby to run into any space between the end portion of each maintube to be connected and the associated end portion of the end of theconnector tube. Each joint is thereafter cooled to solidify the bondingmaterial.

BRIEF DESCRIPTION OF THE DRAWING I FIG. 1 is a perspective view of anevaporator or condenser unit constructed in accordance with the methodof the present invention.

FIG. 2 is a somewhat enlarged fragmentary plan view of the remote end ofthe unit of FIG. 1.

FIG. 3 is a somewhat enlarged fragmentary longitudinal sectional viewthrough a tube to be connected and shows the tube after a socket hasbeen formed therein.

FIG. 4 is a somewhat enlarged fragmentary view of a partially completedsocket joint.

FIG. 5 is a fragmentary view showing a completed socket joint.

FIG. 6 is a longitudinal sectional view through the socket joint of FIG.5.

DETAILED DESCRIPTION OF THE PREFERRED METHOD The method of the presentinvention is illustrated with reference to an evaporator or condensercoil particularly adapted for use in refrigeration apparatus.

Referring now to the drawing, and particularly to FIGS. 1 and 2, anevaporator or condenser coil utilizing tubes joined in accordance withthe invention and indicated generally at 10 comprises a plurality ofgenerally similar parallel tin and tube sections connected in seriesbetween a fluid inlet 12 and a fluid outlet 14 to provide a passagewayfor suitable fluid medium. The length and number of sections in a coilmay vary in accordance with the heat transfer requirements of theapparatus with which it is to be used. However, the illustrated coil 10includes four sections, typical sections being generally indicated atl6, 16. Each section 16 includes elongated parallel tubes 18, 18 whichcarry a longitudinal spaced series of transversely disposed heatexchange plates or fins 20, 20. Support plates 22 and 24 receive the endportions of the tubes 18, 18 therethrough and maintain the sections 16,16 in generally parallel relation each to the other and to the other twosections which comprise the coil 10. One or more additional supportplates such as indicated at 26 may be provided, if desired, to engagethe tubes intermediate the fins to impart further rigidity to thestructure.

The tubes 18, 18 in each section 16 are integrally connected in pairs.Specifically, each tube 18 is joined at one end to another tube 18 inthe same section by an integral U-bend portion 28 as shown in FIG. 1. Atits other end each tube 18 is connected to one end of a generallyU-shaped connector tube 30 at a socket joint generally indicated at 32..The other end of the connector tube 30 is joined to another tube in anadjacent section at another joint 32. The tubes 18, 18 and theirassociated connecting tubes 30, 30 are preferably made from aluminum andin the description of operations which follows the present invention isillustrated with particular reference to a method for joining the endsof aluminum tubes.

The coil 10 is assembled by supporting the various plates and fins inaligned and spaced relation while the various tubes are thrusttherethrough. The integrally connected tubes 18, 18 are inserted inpairs through the support plate 22 and have end portions 34, 34 whichextend for some distance beyond the support plate 24. Preferably thefins and tubes are retained in permanently assembled relation byexpanding the tubes after the fins have been positioned thereon. Thisexpansion operation may, for example, be carried out by applying apressure fluid to the tubes and, if desired, the support plates 22, 24,and 26 may also be permanently assembled with the tubes by thisexpansion operation.

Each connector tube 30 has ends of sufficiently less diameter than theends of the tubes to be connected so that each end of the connector tubecan be inserted into an associated end of a tube to be connected. Wherean aluminum soldered joint is to be provided, as in the illustratedcase, it is preferable that the outside diameter of the connecting tube30 be from 0.010 to 0.030 inches smaller than the inside diameter ofeach associated tube 18 to be connected to insure formation of a soundjoint.

The progressive steps for making a typical socket joint 32 areillustrated in FIGS. 3-6. A socket 36 is first provided in the endportion 34 by forming a radially inwardly directed bead 38 on the tube18 spaced from the end thereof. The bead is formed by rolling orotherwise forming an external groove 40 in the tube 18 either before orafter the tube has been assembled with the various fins and supportplates. The socket 36 has a lip 42 which is provided by applying asuitable tool to the end of the tube 18 to widen or slightly flare theopen end thereof so that the end of the connector tube 30 may be easilyinserted therein.

At this point it should be noted that the socket 30 is formed withoutexposing the interior surface thereof beyond the lip 42 to contact witha forming or expanding tool or the like. Thus, the interior surface ofthe socket 36 retains its mill stock finish. It should be further notedthat each end portion of the connector tube 30 also retains a mill stockfinish, since no forming operations are performed thereon. A mill stockfinish is generally free of embedded impurities and does not requireabrasive type cleaning preparatory to soldering, therefore, in theexercise of the present method such cleaning operations are unnecessary.However, for best results it is desirable to preclean the surfaces to bejoined to remove any surface oil, grease, or other foreign matter andfor this purpose a suitable hydrocarbon solvent is preferably used.

A suitable flux is preferably applied to the surfaces to be joined andthis operation may be most conveniently performed before the connector30 is inserted into the socket 38. A reactive flux of the zinc chloridebase type is preferably employed.

The connecting tube 30 is inserted into the socket 36 to bring the endthereof into abutting relation with the head 38 as shown in FIG. 6.Thereafter, a ring of thermal fluid welding material or aluminum solder44 is applied to the flared end of the tube 18 and around the connectingtube 30, the position of the solder ring being shown in FIG. 4. Sincethe capillary action of the aluminum solder is generally poor, it isdesirable to support the tube 18 in a generally axially verticalposition before sufficient temperature is applied to melt the solder andrun it into the space between the associated end portions of the tubes.

The narrow spread between the melting ranges of aluminum solder andaluminum alloys make control of soldering temperature amdnatory. Thehigh thermal conductivity of aluminum requires rapid application of heatin order to insure adequate temperature in the area to be soldered.Preferably a soldering temperature in the range of 720 and 800 F ismaintained. The soldering operation may be carried out in various waysas,

for example, by radiant heating, electrical resistance heating or by thecontrolled application of a torch. However, in accordance with onepreferred method of practicing the invention the joints 32, 32 areheated by applying an induction heating means.

The solder will displace the flux as it runs into the joint, therebycausing some flux residue in the tubes. Due to the corrosive nature ofthe flux this residue must be removed after the joint has cooledsufficiently to achieve fluid tight solidification of the weldingmaterial with the associated end portions of the tubes. This fluxresidue is preferably removed by circulating a suitable washing fluidthrough the connected tube structure. Water at a temperature of at leastF has proven generally effective for this purpose. However, if theamount of flux residue formed is heavy it may be desirable to circulatea 5 percent ammonia solution through the tube structure to effect thiscleaning operation.

While the method of the present invention had been illustrated withreference to aluminum tube joint constructions it should be understoodthat the aforedescribed method may be advantageously employed to jointubes made from other materials. More particularly, the present methodis applicable to constructions wherein the end portions of tubes are tobe connected at bonded joints and wherein it is desired that theassociated joint surfaces to be bonded together be substantially free ofembedded impurities. Thus,joint constructions made from aluminum orother tubing and secured by a suitable bonding material, as, forexample, a thermo setting resin or epoxy compound may be made inaccordance with the present method and such constructions arecontemplated within the scope of the invention. Where a thermo settingbonding compound is used a temperature will generally be applied to flowthe bonding material in the joint and to cure it. However, thistemperature will generally be somewhat lowered than the temperatureapplied when a solder or like welding material is employed.

A preferred method for practicing the invention is illustrated anddescribed, but it will be understood that various changes may be madefrom the method disclosed and that the drawings and description are notto be construed as defining or limiting the scope of the invention, theclaims forming a part of this specification being relied upon for thatpurpose.

I claim:

1. In a method for making an evaporator or condenser construction forrefrigeration apparatus the steps of providing at least two elongatedmain metal tubes defining a plurality of main tube ends, each of saidmain tubes having substantially uniform inside and outside diametersthroughout the length thereof and having a mill stock finish, providingat least one generally U-shaped connector tube having substantiallyunifonn inside and outside diameters throughout the length thereof and amill stock finish and defining a pair of connector tube ends, said maintube ends and said connector tube ends having such relative inside andoutside diameters that said U-shaped connector tube may have each of itstwo tube ends telescopically assembled with an associated one of saidmain tube ends to form a connection consisting of two joints eachinvolving one tube end inserted in another tube end, thrusting said maintubes through heat exchanged plates and in general parallel relation,forming only a radially inwardly directed head on the larger diametertube end of each proposed joint and which bead is spaced from theadjacent open end of said larger diameter tube end to define a socketbetween said open end and said bead, said socket having an insidediameter equal to the inside diameter of the remainder of the tube inwhich it is formed and an interior surface having a mill stock finish,assembling each tube end of said connector tube telescopically with anassociated one of the pair of the pair of main tube ends to bring thesmaller diameter tube end of each joint into abutting relation with anassociated bead, applying a solder bonding material around each endportion of said smaller diameter tube end of each joint and generallyadjacent the open end of said larger diameter tube end of each joint,heating each joint to cause said bonding material to flow and thereby torun it into any space between the end portion of each tube to beconnected and the associated end portion of the end of the connectortube and cooling each joint to achieve fluid type solidification of thebonding material.

2. The method as set forth in claim 1 wherein the stop of forming only aradially inwardly directed head is further characterized as forming saidbead on each of said main tubes.

3. The method as set forth in claim 1 wherein the step of forming aradially inwardly directed bead is further characterized as rolling anexternal groove on the larger diameter tube end of each proposed jointspaced from the adjacent open end thereof.

4. The method as set forth in claim 1 including the additional step ofapplying a tool to said open end of said larger diameter tube end toflare said open end thereof to receive said smaller diameter tube andeasily.

5. The method set forth in claim 4 wherein the step of applying saidbonding material is further characterized as applying said bondingmaterial to the flared end of said larger diameter tube end and aroundsaid smaller diameter tube end.

6. The method set forth in claim 5 including the additional step ofapplying flux to the exterior surface portion of said other tube and theinterior surface portion of said one tube at the end portions thereofbefore the step of applying said bonding material, and circulatingwashing fluid through the connected tubes to remove excess fluxtherefrom after the step of heating.

7. The method as set forth in claim 4 including the additional step ofsupporting said main tubes in an axially vertical position before thestep of heating each 'oint.

J 8. The method as set forth in claim 1 wherein the step of heating isfurther characterized as heating each joint with induction heatingmeans.

9. The method as set forth in claim 1 wherein said tubes are aluminumand including the additional step of cleaning the associated endportions of said tubes with a hydrocarbon solution.

l I l i UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3 750,- 248 Deted August 7 1973 Inventor(s) Herbert I'I'iS It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

C01. line63, "amdnatory"shou1d be -mandatory--.

Col. line 19, "had" should be --has-.

line; 9-, delete "of the pair" (second occurrence) Col. 4, line 37,"lowered" should be --lower--.

5, line 21', "stop" should be --step--.

C01. line 4, "and" should be --end--.

Signed and sealed this 30th day of July 1971}.

(SEAL) Attest:

MCCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

1. In a method for making an evaporator or condenser construction forrefrigeration apparatus the steps of providing at least two elongatedmain metal tubes defining a plurality of main tube ends, each of saidmain tubes having substantially uniform inside and outside diametersthroughout the length thereof and having a mill stock finish, providingat least one generally U-shaped connector tube having substantiallyuniform inside and outside diameters throughout the length thereof and amill stock finish and defining a pair of connector tube ends, said maintube ends and said connector tube ends having such relative inside andoutside diameters that said U-shaped connector tube may have each of itstwo tube ends telescopically assembled with an associated one of saidmain tube ends to form a connection consisting of two joints eachinvolving one tube end inserted in another tube end, thrusting said maintubes through heat exchanged plates and in general parallel relation,forming only a radially inwardly directed bead on the larger diametertube end of each proposed joint and which bead is spaced from theadjacent open end of said larger diameter tube end to define a socketbetween said open end and said bead, said socket having an insidediameter equal to the inside diameter of the remainder of the tube inwhich it is formed and an interior surface having a mill stock finish,assembling each tube end of said connector tube telescopically with anassociated one of the pair of the pair of main tube ends to bring thesmaller diameter tube end of each joint into abutting relation with anassociated bead, applying a solder bonding material around each endportion of said smaller diameter tube end of each joint and generallyadjacent the open end of said larger diameter tube end of each joint,heating each joint to cause said bonding material to flow and thereby torun it into any space between the end portion of each tube to beconnected and the associated end portion of the end of the connectortube and cooling each joint to achieve fluid type solidification of thebonding material.
 2. The method As set forth in claim 1 wherein the stopof forming only a radially inwardly directed bead is furthercharacterized as forming said bead on each of said main tubes.
 3. Themethod as set forth in claim 1 wherein the step of forming a radiallyinwardly directed bead is further characterized as rolling an externalgroove on the larger diameter tube end of each proposed joint spacedfrom the adjacent open end thereof.
 4. The method as set forth in claim1 including the additional step of applying a tool to said open end ofsaid larger diameter tube end to flare said open end thereof to receivesaid smaller diameter tube and easily.
 5. The method set forth in claim4 wherein the step of applying said bonding material is furthercharacterized as applying said bonding material to the flared end ofsaid larger diameter tube end and around said smaller diameter tube end.6. The method set forth in claim 5 including the additional step ofapplying flux to the exterior surface portion of said other tube and theinterior surface portion of said one tube at the end portions thereofbefore the step of applying said bonding material, and circulatingwashing fluid through the connected tubes to remove excess fluxtherefrom after the step of heating.
 7. The method as set forth in claim4 including the additional step of supporting said main tubes in anaxially vertical position before the step of heating each joint.
 8. Themethod as set forth in claim 1 wherein the step of heating is furthercharacterized as heating each joint with induction heating means.
 9. Themethod as set forth in claim 1 wherein said tubes are aluminum andincluding the additional step of cleaning the associated end portions ofsaid tubes with a hydrocarbon solution.